Carburetor with automatic choke

ABSTRACT

In a carburetor equipped with an automatic choke, the throttle valve and choke valve are linked through a spring and link mechanism whereby the opening of the choke is controlled in accordance with the position of the throttle operating through changes in the spring tension of the interconnecting spring mechanism occurring with the opening of the throttle.

United States Patent 11 1 Nakada et al. 1 June 3, 1975 CARBURETOR WITHAUTOMATIC CHOKE 1,896,390 2/1933 Carter 123/119 F 2,094,165 9/1937Bicknell.... 26l/52 [75] Inventors: Masahllw Nakada? 2,134,421 10/1938Sisson 123/119 F Matsumoto; Nobuyuki Kobayashi, 2,427,030 9/1947 Swigert123/119 F all of Toyota, Japan 2,464,328 3/ 1949 Mallory 261/52Assigneez Toyota Jidosha gy Kabushiki 2,977,100 3/1961 Carlson 261/52Kaisha, Japan [22] Filed: June 5, 1973 Primary Examiner-Wendell E. BurnsAttorney, Agent, or Firm-Toren, MCgredy & Stanger [21] Appl. No.:367,220

[30] Foreign Application Priority Data [57] ABSTRACT July 13, 1972 Japan47-69620 In a carburetor equipped with an automatic choke, the 123/119261/39 C; 261/52 throttle valve and choke valve are linked through a[51] Int. Cl. F02m 1/10; F02m l/O2 Spring and link mechanism whereby theOpening f the Flew of Search 261/52, 39 C, 39 B, 39 R, choke iscontrolled in accordance with the position of 261/64 E; 123/119 F thethrottle operating through changes in the spring tension of theinterconnecting spring mechanism oc- References C'ted curring with theopening of the throttle.

UNITED STATES PATENTS 1,456,502 5/1933 Hartwell 261/52 1 Claim, 6Drawing Figures PATENTEUJUNIS ms SHEET FIG. 2

FIG.

FIG. 3

THROTTLE OPENING- LARGE THROTTLE OPENING SMALL TIME PATENTEDJUN3 SHEETFIG. 6

02- mum ll O FULLY CLOSED -FULLY OPENED THROTTLE OPENING CARBURETOR WITHAUTOMATIC CHOKE BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to an automatic, choke of hot air type forautomotive vehicles in which a thermostatic coil operates in response toair heated by the exhaust gas to control the choke valve, and morespecifically the invention relates to a novel and useful carburetorequipped with such an automatic choking mechanism.

2. Description of the Prior Art Usually automotive engines duringinitial warm-up require a richer air-fuel mixture and hence a greaterchoking effect for idling or low-speed light-load operation than for theother phases of engine operation. It has, however, been difficult toattain an optimum choking effect for every phase of engine operationwith conventional automatic chokes because they are generally socontrolled that they open the choke valve in response to highintake-manifold vacuum.

The present invention has for its object the provision of a carburetorequipped with an automatic choke free of the foregoing disadvantage,which is designed so that when the throttle is partly open the forcewith which the choke valve is closed will be intensified so that anincreased choking effect is achieved during idling or low-speedlight-load operation.

SUMMARY OF THE INVENTION Briefly, the present invention may be describedas a carburetor assembly which is equipped with an automatic choke andwhich includes a choke valve controlled by thermostatic means responsiveto the exhaust gas temperatures of the vehicle upon which the carburetoris mounted, said exhaust gas temperatures being utilized for controllingoperation of the choke valve. More particularly, the present inventioncomprises the improvement wherein a control system is incorporated intothe carburetor assembly whereby the choke valve may be controlled inresponse to the position of the throttle valve as well as by thethermostatic control means. In the present invention, a link mechanismoperating in conjunction with said thermostatic means operates to rendersaid choke valve responsive to the po-' sition of the throttle valve.The link mechanism includes spring means operatively interconnecting thethrottle valve and the choke valve to render the position of the chokevalve dependant upon the position of the throttle valve. The springmeans are positioned to effect a smaller choke opening with smallerthrottle openings through variation in the tension of the spring meansthereby enabling variations in the position of the throttle valve toinfluence the position of the choke valve.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a carburetorwhich an automatic choke embodying the present invention;

FIG. 2 is a view similar to FIG. 1, showing the carburetor during adifferent phase of its operation;

FIG. 3 is a characteristic curve of the operation of the embodimentshown in FIG. 1;

FIG. 4 is a side view of another embodiment of the invention;

FIG. 5 is a front view of the embodiment of FIG. 4; and

FIG. 6 is a characteristic curve of the operation of the embodimentshown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will bebetter understood from the following detailed description taken inconjunction with the accompanying drawings showing preferred embodimentsthereof.

Referring first to FIG. I, there is shown a carburetor body 1, a chokevalve 2, a choke shaft 3, a throttle valve 4, and a throttle shaft 5.Levers 6, 7 and 8 are formed as a unitary member secured to the chokeshaft 3. The lever 6 is connected to the outer end of a spiraledbimetallic spring or theremostatic coil ,9, the inner end of which isfixed to a theremostat housing 10. The lever 8 is connected to aconnecting rod 11, the other end of which is connected to a vacuumpiston (not shown) in a choke cylinder 12. A lever pin 13 is fixedlyanchored in the thermostat housing 10, and a spring lever 14 ispivotally supported by the pin 13 for smooth turning motion. One end ofthe spring lever is connected to the lever 7 by a spring 15. Thethrottle shaft 5 fixedly supports a throttle lever 16, which in turn islinked to a push rod 17 through a connecting rod 18. A guide 19 isprovided for the push rod, and a stopper 20 for the spring lever 14.

With the construction above described, the carburetor equipped with theautomatic choke according to the present invention operates in thefollowing manner. Before the engine warms up, the choke is kept openedin the position where three forces are in equilibrium. These forces are(l) the force with which the thermostatic coil 9 tends to close thechoke valve 2, (2) the force with which the connecting rod 11 tends toopen the choke valve 2 via the lever 8 in response to the manifoldvacuum applied on the underside of the vacuum piston, and (3) the forcewith which the spring 15 tends to close the choke valve 2.

When the engine is idling or running at low speed under light load, thethrottle is slightly open as shown in FIG. 1, and the push rod 17 turnsthe spring lever 14 clockwise. As the end of the spring lever 14connected to the spring 15 moves downward, the urging of the spring 15to close the choke valve 2 increases, with a consequent decrease in theopening of the choke valve.

With the increase of the engine load, as shown in FIG. 2, the throttlevalve 4 opens wider, causing the throttle lever 16 to turncounter-clockwise and thereby bring the push rod 17 downward through theguide 19. As a consequence the spring lever 14 turns counterclockwiseuntil it hits the stopper 20. With the spring lever 14 kept in thisposition, its end connected to the spring 15 is at a level higher thanin FIG. 1. Naturally, the tendency of the spring 15 to close the chokevalve 2 weakens, and the choke valve opens wider than in FIG. 1.

As will be appreciated from the foregoing, it is possible to change thetension of the spring 15 by operatively associating the spring lever 14with the opening of the throttle so that, while the throttle opening issmall, the force with which the choke valve 2 is closed is increased,and vice versa.

Thus, during gradual warm-up of the engine after start, as shown in FIG.3, a greater choking effect is achieved while the throttle opening issmall, with the choking effect being decreased with an increase of thethrottle opening.

As noted above. according to this invention, a spring whose tensionvaries with the opening of the throttle is installed in a conventionalcarburetor equipped with an automatic choke, whereby the choke openingis limited and a good choking effect is attained while the throttleopening is small. This enables the engine to be supplied with a mixtureof an adequate air-fuel ratio during the initial stage of idling justafter a cold start or during idling operation or low-speed light-loadoperation before warm-up. In this way smooth engine operation isensured. When the opening of the throttle is large enough to requireonly a small choking effect. the choke opening can be increased tolessen the choking effect and feed a leaner mixture to the enginethereby reducing the noxious contents of the exhaust emissions.

Another embodiment of the invention will now be described with referenceto FIGS. 4 and 5, wherein like parts as used in FIGS. 1 and 2 aredesignated by like numerals. In this embodiment, a spring stop 21 isfixed to the choke shaft 3, and a choke arm 22 having a cylindrical part22a is revolvably sleeved over the choke shaft 3. One end 15'a of a coilspring 15' is hooked on the stop 21, and the other end 15'b is hooked ona spring stop 22b of the choke arm 22. When the throttle and choke arein the positions shown in FIG. 5, the spring 15' is of suchcharacteristic that it will not apply any force on the spring stop 21and choke arm 22. A spring stop 23 is fixed onto the throttle shaft 5,and a throttle lever 16' having an arcuate slot 16a is revolvablymounted on the throttle shaft 5. One end 24a of a coil spring 24stronger than the spring 15 is hooked on the spring stop 23, and theother end 2412 of the spring is hooked on a spring-stop recess l6'b ofthe throttle lever 16'. The throttle lever 16' and choke arm 22 areconnected via a link 18. The lower end of the link 18' is engaged withthe arcuate slot 16a of the throttle lever 16'. A stopper 25 is providedfor the throttle lever 16'.

Before the engine starts, the opening of throttle valve 4 is small asshown in FIG. 5. The choke valve 2 is almost closed, and the choke arm22, throttle lever 16', and link 18' are in the positions shown, thethrottle valve 4 exerting no force at all on the choke valve 2.

As the throttle valve 4 in the carburetor of the foregoing constructionis turned open counter-clockwise, a rotational force is exerted on thethrottle lever 16 via the spring 24, thus also turning the throttlelever 16 in the same direction. Until the extremity of the slot 16'a ofthe throttle lever 16 comes into contact with the link 18', the throttlevalve 4 will not exert force upon the choke valve 2. As the throttlevalve 4 is further turned open counter-clockwise, the link 18' is pulleddownward and the choke arm 22 is also turned counter-clockwise. Sincethe choke arm 22 and choke shaft 3 are connected via the spring 15, thechoke shaft 3 is also subjected to the counter-clockwise rotationalforce. In other words, the choke valve 2 is subjected to a force thattends to move it to the open position. As the throttle opening isfurther increased, the force inducing the choke valve 2 to open isgradually increased. The throttle lever 16' continues to turncounter-clockwise until it hits the stopper 25, where it no longer turnsbut, because the throttle shaft 5 and throttle lever 16 are connectedwith the spring 24, further opening of the throttle valve 4 is not inthe least constrained. After the throttle lever 16' has contacted thestopper 25, further opening of the throttle valve 4 will not increasethe force urging open the choke valve 2. Thus, the relationshipillustrated in FIG. 6 is established between the throttle opening andthe opening of the choke with the aid of spring force.

From the foregoing it will be appreciated that, in accordance with thepresent invention, a choke opening conforming to the characteristic of aconventional carburetor with an automatic choke is attained when thethrottle opening is relatively small and that a larger choke openingthan with the conventional carburetor is obtained when the throttleopening is relatively large. For example, the second embodiment of theinvention just described exhibits the characteristic graphicallyrepresented in FIG. 3.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the inventiveprinciples, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. In a carburetor assembly having a throttle valve and equipped with anautomatic choke including a choke valve, and thermostatic meansresponsive to exhaust gas temperature for controlling operation of saidchoke valve, the improvement including means for rendering operation ofsaid choke valve dependent upon the position of said throttle valve,said improvement comprising, in combination,

a choke valve shaft connected with said choke valve to rotateconcurrently with displacement thereof,

a throttle valve shaft connected with said throttle valve to rotateconcurrently with displacement thereof,

a throttle lever revolvably mounted upon said throttle valve shaft,

a choke arm revolvably mounted upon said choke valve shaft,

means defining a slot in said throttle lever,

a linkage arm connected between said choke arm and said slot in saidthrottle lever,

a choke valve coil spring, concentrically located about said choke valveshaft and having a pair of ends, with one of said ends connected toimpart a spring force to said choke valve shaft and with the other ofsaid ends being connected to said choke arm, and

a throttle valve coil spring concentrically located about said throttlevalve shaft and having a pair of ends, one of said ends being connectedwith said throttle valve shaft and the other of said ends beingconnected with said throttle lever.

said slot in said throttle lever being configured to impart a force fromsaid throttle lever to said linkage arm only after said throttle leverhas reached a predetermined position by displacement of said throttlevalve beyond a predetermined location.

1. In a carburetor assembly having a throttle valve and equipped with anautomatic choke including a choke valve, and thermostatic meansresponsive to exhaust gas temperature for controlling operation of saidchoke valve, the improvement including means for rendering operation ofsaid choke valve dependent upon the position of said throttle valve,said improvement comprising, in combination, a choke valve shaftconnected with said choke valve to rotate concurrently with displacementthereof, a throttle valve shaft connected with said throttle valve torotate concurrently with displacement thereof, a throttle leverrevolvably mounted upon said throttle valve shaft, a choke armrevolvably mounted upon said choke valve shaft, means defining a slot insaid throttle lever, a linkage arm connected between said choke arm andsaid slot in said throttle lever, a choke valve coil spring,concentrically located about said choke valve shaft and having a pair ofends, with one of said ends connected to impart a spring force to saidchoke valve shaft and with the other of said ends being connected tosaid choke arm, and a throttle valve coil spring concentrically locatedabout said throttle valve shaft and having a pair of ends, one of saidends being connected with said throttle valve shaft and the other ofsaid ends being connected with said throttle lever, said slot in saidthrottle lever being configured to impart a force from said throttlelever to said linkage arm only after said throttle lever has reached apredetermined position by displacement of said throttle valve beyond apredetermined location.